نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Hypereutectic Al-Si composites due to their low density and desirable properties have attracted a great amount of interest by the automotive and aerospace industries. However, the coarse size and un-modified morphology of the primary silicon particles that usually forms during the solidification of these alloys impose negative effects on the mechanical properties of these composites. Therefore, it is necessary to choose a suitable casting and solidification technique to overcome this drawback. In the present study, the vibrating cooling slope (VCS) technique as a semi-solid casting process was employed for preparation of composites by using the hypereutectic Al-20wt.%Si ingot as the starting material. The ingot melted and superheated at 50, 70 and 100 °C and after passing a cooling slop poured into a cast iron mold. For the purpose of comparison composite samples by using the conventional cooling slope (CS) and gravity casting (GC) also prepared by applying the identical materials and superheating temperatures as the VCS samples. The effect of the superheating temperatures on the microstructure, porosity and hardness of the composites investigated. A set of samples subjected to pin-on-disc wear test. The increased superheating temperature resulted in increased size of the Si particles for all the investigated samples. The CS samples despite of their higher porosity exhibited higher hardness values as compared with their GC counterparts. Also the hardness of VCS samples was higher than their CS counterparts. The wear test results confirmed the decreased both the wear loss and friction coefficient for the VCS samples
کلیدواژهها English
